Cellulose is a polysaccharide having 50 to 1000 or more glucose molecules linked together by β-glycosidic bond, and is also a main component of so-called wood-based biomass such as wood pulp or cotton. Studies for practical use of saccharides obtained by hydrolyzing cellulose, particularly, water-soluble oligosaccharides such as glucose as a raw material in manufacturing bioethanol through alcohol fermentation have been conducted in recent years (see PTL 1).
Generally, cellulose is insoluble in water and also hardly dissolves in an alkali aqueous solution. However, several solvents which can dissolve cellulose are known. For example, when cellulose is treated with a sodium hydroxide aqueous solution, a sodium salt of the cellulose is formed. When this salt is mixed with carbon disulfide, the mixture becomes sodium cellulose xanthate and becomes a colloidal dispersion solution which is referred to as viscose. Spun viscose rayon is formed by extruding the viscose into sulfuric acid. The cellulose constituting the viscose rayon has the same chemical composition as natural cellulose.
In addition, cellulose is also soluble in a cuprammonium solution. By extruding it into an acidic aqueous solution, cuprammonium rayon can be spun (see PTL 2).
In conventional cellulose solution manufacturing methods, carbon disulfide or a cuprammonium solution is used, and thus it is necessary to process waste water and the like, which causes a problem in that the environmental burden increases. In addition, when it is necessary to prevent the chemical substances from remaining in reproduced cellulose (rayon) to be obtained, it is also necessary to perform a rinsing treatment using a large amount of water.